What Borg UI Does With Your Data

Borg UI holds the keys to your backups. Before you install it, you should know what it keeps, what it protects, and what it sends anywhere else.

Everything on this page is checkable. Borg UI is AGPL-3.0 and the whole source tree is public, so every claim below names the file that implements it. If a claim and the code disagree, the code is right and this page is a bug.

For hardening a deployment (TLS, the Docker socket, reverse proxies, /metrics), see Security. This page is about the software itself.

Secrets Are Encrypted At Rest

Your Borg repository passphrase is encrypted in the database, not stored in plain text. So are the other secrets the app holds:

Secret	Where
Borg repository passphrase	repositories.passphrase
SSH private keys	SSH key storage
Two-factor (TOTP) secrets	users.totp_secret_encrypted
OIDC client secret and cached ID tokens	OIDC settings, session rows
Cloud provider OAuth client secrets	Google Drive, OneDrive settings
Password-type script parameters	Script parameter values

Encryption is Fernet (AES-128-CBC with an HMAC), keyed from the instance's SECRET_KEY. See EncryptedString in app/database/models.py and encrypt_secret in app/core/security.py.

What this protects against: someone who reads a copy of the database, such as a stolen backup of /data, a leaked volume snapshot, or an SQL injection that dumps a table.

What it does not protect against: someone who has your whole /data directory. The key is derived from SECRET_KEY, which is generated into /data on first boot, so an attacker holding all of /data holds the key as well. Treat /data as being exactly as sensitive as the backups it can restore, and set SECRET_KEY yourself if you want the key to live somewhere else.

SSH Hosts Are Verified

Every SSH connection Borg UI makes verifies the remote host's key. Connecting to a machine whose key does not match the one on record fails; it is never accepted silently.

The model is OpenSSH's own trust on first use:

• New connections. When you add a remote machine, Borg UI shows you the host's fingerprint and asks you to confirm it before storing it. The fingerprint shown matches ssh-keygen -lf /etc/ssh/ssh_host_ed25519_key.pub on the host exactly, so you can compare the two.
• Connections that predate this feature. Those were already running with no verification at all. Rather than break every existing install on upgrade, the key in use is recorded on first contact after the upgrade.
• Either way, a key that changes later is refused and you have to re-verify before the connection works again.

The recorded key is stored on the connection row and is visible in the UI, so you can see what your instance trusts. See app/utils/ssh_host_keys.py.

Before this shipped, every SSH invocation passed StrictHostKeyChecking=no with UserKnownHostsFile=/dev/null, meaning anything that answered on the address was trusted. If you are running an older version, upgrade.

What Leaves Your Machine

Two things, both of which you can see and control.

The license service

Your instance talks to a license service to activate the 30-day full access period, to check a license key you entered, and to refresh entitlement state afterward. The endpoint defaults to https://license.borgui.com and is overridable with ACTIVATION_SERVICE_URL, so if you want to see the traffic or block it, point that at your own host or firewall the one you configured.

Four requests exist, and this is every field each one sends (app/services/licensing_service.py):

Request	Fields
Full access activation (/v1/trials/activate)	instance_id, app, app_version, hostname, fingerprint, requested_plan
Entitlement refresh (/v1/entitlements/refresh)	instance_id, current_entitlement_id, app_version
License activation (/v1/licenses/activate)	instance_id, license_key, app_version
License deactivation (/v1/licenses/deactivate)	instance_id, license_id

instance_id is a random id generated on your instance. hostname is the container's HOSTNAME environment variable, and it is sent only by the first request. No authentication headers are attached to any of them.

Nothing else is in these requests: no repository names, no paths, no archive contents, no file names, no user accounts, and no email addresses.

Community does not need a license key and no feature is gated behind reaching this service. If it is unreachable, Borg UI keeps working.

To stop the contact entirely, set:

ENABLE_STARTUP_LICENSE_SYNC=false

That covers both the call at startup and the hourly refresh, so the instance stops contacting the service on its own. Plan upgrades and full-access activation then cannot refresh automatically.

What remains is only contact you start yourself: entering a license key, refreshing it, or removing it from Settings, all admin-only actions that do nothing until you take them. If you want an instance that cannot reach the service at all, block it at your firewall.

Usage analytics

The web UI loads Umami to count page views and feature usage. It starts on, and a banner on first login asks whether to keep it. Declining stops it from that point, and you can change the answer whenever you like in Settings > Preferences. Page views from that first session, before you answer the banner, are counted.

Before anything is sent, your real hostname and URL are replaced with app.borgui, so your private DNS names and IP addresses do not leave the browser. The script tag is loaded with referrerpolicy="no-referrer" so the request that fetches it cannot carry the origin either. The identifier attached to a session is a hash of your install id and username, not the username itself. The session also carries your app version and your plan name (community, pro, or enterprise) so usage can be compared across plans. No licence key, customer, or other billing detail is sent. See frontend/src/utils/analytics.ts and Analytics.

Nothing else phones home. No crash reporting, no error telemetry, no update beacon.

What never leaves

Your backup data. Borg UI runs borg against your repositories on your infrastructure. Archive contents, file names, and repository paths are never transmitted anywhere. There is no cloud component in the backup path.

Your Keys Keep Working

• Borg UI is AGPL-3.0. You can read it, fork it, patch it, and run your fork.
• Repositories are ordinary Borg repositories. If Borg UI disappears tomorrow, borg list, borg extract, and borg mount still work against them from the command line. There is no proprietary format and no lock-in.
• A license key is a signed document validated on your instance. It is not a runtime permission slip fetched from us on every action.

Reporting a Vulnerability

Report security issues privately through GitHub security advisories rather than a public issue.